Structure and method to form III-V, Ge and SiGe fins on insulator

ABSTRACT

A method provides a first substrate supporting an insulator layer having trenches formed therein; filling the trenches using an epitaxial growth process with at least semiconductor material; planarizing tops of the filled trenches; forming a first layer of dielectric material on a resulting planarized surface; inverting the first substrate wafer to place the first layer of dielectric material in contact with a second layer of dielectric material on a second substrate; bonding the first substrate to the second substrate through the first and second layers of dielectric material to form a common layer of dielectric material; and removing the first substrate and a first portion of the filled trenches to leave a second portion of the filled trenches disposed upon the common dielectric layer. The removed first portion of the filled trenches contains dislocation defects. The method then removes the insulator layer to leave a plurality of Fin structures.

TECHNICAL FIELD

The embodiments of this invention relate generally to semiconductordevices and fabrication techniques and, more specifically, relate to thefabrication of semiconductor transistor devices including FINFETs. Theembodiments of this invention also relate to aspect ratio trapping andwafer bonding techniques.

BACKGROUND

For more than three decades, the continued miniaturization of metaloxide semiconductor field effect transistors (MOSFETs) has driven theworldwide semiconductor industry. Various impediments to continuedscaling have been predicted for decades, but a history of innovation hassustained Moore's Law in spite of many challenges. However, there aregrowing signs today that metal oxide semiconductor transistors arebeginning to reach their traditional scaling limits. Since it has becomeincreasingly difficult to improve MOSFETs and therefore complementarymetal oxide semiconductor (CMOS) performance through continued scaling,the development of further methods for improving performance, inaddition to scaling, has become critical. One such method involves usinghigh mobility materials, other than silicon, for CMOS such as GroupIII-V semiconductors or SiGe or Ge.

Methods for fabricating Fin structures on an insulator structure (wherethe Fin can be composed of, for example, SiGe, Ge, and Group III-Vsemiconductor materials) are currently being explored. In those caseswhere wafer bonding techniques are used followed by Fin patterning aproblem can arise that is related to a presence of crystalline defectsin the Fin material. Another problem area relates to Fin patterningissues such as Fin taper, Fin sidewall roughness, reactive ion etching(RIE) damage and post RIE cleaning.

SUMMARY

In a first aspect thereof the embodiments of this invention provide amethod that comprises providing a first substrate supporting aninsulator layer having trenches formed therein; filling the trenchesusing an epitaxial growth process with at least one type ofsemiconductor material; planarizing tops of the filled trenches andforming a first layer of dielectric material on a resulting planarizedsurface; inverting the first substrate wafer to place the first layer ofdielectric material in contact with a second layer of dielectricmaterial disposed on a second substrate; bonding the first substrate tothe second substrate through the first layer of dielectric material andthe second layer of dielectric material to form a common layer ofdielectric material; removing the first substrate and a first portion ofthe filled trenches to leave a second portion of the filled trenchesdisposed upon the common layer of dielectric material, where the firstportion of the filled trenches contains dislocation defects in thesemiconductor material resulting from the epitaxial growth process; andremoving the insulator layer to leave a plurality of Fin structuresdisposed upon the common layer of dielectric material, where each Finstructure corresponds to one of the filled trenches.

In another aspect thereof the embodiments of this invention provide astructure that comprises an upper surface and a lower surface. The uppersurface is a first surface of a first substrate and the lower surface isa first surface of a second substrate. The structure further comprises alayer of insulator material having a first surface and a second surfaceopposite the first surface, where the first surface of the layer ofinsulator material is disposed on a second surface of the firstsubstrate that is opposite the first surface of the first substrate. Thelayer of insulator material has a plurality of trenches formed thereinthat extend through the layer of insulator material from the secondsurface of the layer of insulator material to the first surface of thelayer of insulator material. The trenches are filled at least one typeof semiconductor material. The structure further includes a dielectriclayer disposed between the second surface of the layer of insulatormaterial and a second surface of a second substrate that is opposite tothe first surface of the second substrate. In the structure thesemiconductor material that fills the trenches contains dislocationdefects that are primarily concentrated at and near to the secondsurface of the first substrate.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 shows in enlarged cross-sectional views (not to scale) anoverview of a procedure to fabricate Fins composed of a Group III-Vmaterial on an insulating substrate.

FIG. 2 illustrates a first step of a method in accordance with thisinvention where a seed wafer and a handle wafer are provided.

FIG. 3 shows the formation on the seed wafer of an insulator stripepattern for ART (aspect ratio trapping) in preparation for semiconductormaterial epitaxy.

FIG. 4 illustrates a selective epitaxial growth (SEG) process to grow adesired semiconductor material in the trenches that define the ARTinsulator stripe pattern.

FIG. 5 shows a result of a selective removal of a top-most portion of adielectric layer 32 and the semiconductor material that fills thetrenches.

FIG. 6 shows a result of a deposition of a dielectric film over apolished top of the seed wafer structure.

FIG. 7 shows a result of a wafer bonding operation wherein the seedwafer structure formed in FIGS. 2-6 is inverted and a top surface of thedielectric film is placed in contact with and bonded to a top surface ofthe handle wafer BOX layer.

FIG. 8 illustrates a material removal operation that removes thesubstrate of the seed wafer and that portion of the ART epitaxy andtrenches containing dislocation defects to obtain a desired Fin height.

FIGS. 9A-9D, collectively referred to as FIG. 9, illustrate anembodiment further in accordance with this invention where each channelFin material can be chosen for NFET and PFET as needed.

DETAILED DESCRIPTION

The word “exemplary” is used herein to mean “serving as an example,instance, or illustration.” Any embodiment described herein as“exemplary” is not necessarily to be construed as preferred oradvantageous over other embodiments. All of the embodiments described inthis Detailed Description are exemplary embodiments provided to enablepersons skilled in the art to make or use the invention and not to limitthe scope of the invention which is defined by the claims.

The terms “epitaxial growth and/or deposition” and “epitaxially formedand/or grown” mean the growth of a semiconductor material on adeposition surface of a semiconductor material, in which thesemiconductor material being grown has the same crystallinecharacteristics as the semiconductor material of the deposition surface.In an epitaxial deposition process, the chemical reactants provided bysource gases are controlled and the system parameters are set so thatthe depositing atoms arrive at the deposition surface of thesemiconductor substrate with sufficient energy to move around on thesurface and orient themselves to the crystal arrangement of the atoms ofthe deposition surface. Therefore, an epitaxial semiconductor materialhas the same crystalline characteristics as the deposition surface onwhich it is formed. For example, an epitaxial semiconductor materialdeposited on a {100} crystal surface will take on a {100} orientation.In some embodiments, epitaxial growth and/or deposition processes areselective to forming on semiconductor surface, and do not depositmaterial on dielectric surfaces, such as silicon dioxide or siliconnitride surfaces.

Examples of various epitaxial growth process apparatuses that aresuitable for use in implementing the embodiments of this inventioninclude, but are not limited to, rapid thermal chemical vapor deposition(RTCVD), low-energy plasma deposition (LEPD), ultra-high vacuum chemicalvapor deposition (UHVCVD), atmospheric pressure chemical vapordeposition (APCVD) and molecular beam epitaxy (MBE). The temperature foran epitaxial deposition process typically ranges from about 550° C. toabout 900° C. Although higher temperature typically results in fasterdeposition, the faster deposition may result in crystal defects and filmcracking.

FIG. 1 shows in enlarged cross-sectional views (not to scale) anoverview of a procedure to fabricate Fins composed of a Group III-Vsemiconductor material on an insulating substrate (one composed in thisexample of a Silicon substrate 12 having an overlying buried oxide (BOX)layer 14). The Silicon substrate 12 and BOX layer can be provided onwhat may be referred to as a handle wafer 10. Also provided is what maybe referred to as a seed wafer 20 having in this non-limiting example aSilicon substrate 22, a suitable buffer layer 24 for Group III-Vmaterial and a layer 26 of a desired Group III-V semiconductor material(e.g., binaries such as, e.g., GaAs, GaP, GaSb, InP, InAs, InSb,tertiaries such as, e.g., InGaAs and quaternaries such as, e.g.,AlInGaP). In other cases the semiconductor material could be, forexample, a Silicon Germanium alloy (SiGe) or Ge.

The seed wafer 20 is inverted and the Group III-V layer 26 is waferbonded to the BOX layer 14 of the handle wafer 10. The Si layer 22 andbuffer layer 24 of the seed wafer 20 are then removed by any suitableprocess, such as Smart Cut® or by grinding and chemical mechanicalpolishing (CMP). The remaining Group III-V layer 26 is thenphotolithographically patterned and etched, such by an RIE procedure, todefine Group III-V Fins 28 that are disposed on the BOX layer 14.Although not shown in FIG. 1, the Fins 28 are then further processed todefine source and drain regions, and suitable gate structures andconductors are formed in order to provide transistors, such as PFETs andNFETs as needed.

However, the resulting Fins 28 are susceptible to the above mentionedproblems related to the presence of crystal defects in the Fins 28 andthe patterning issues related to RIE.

As will be described with reference to FIGS. 2-9 the exemplaryembodiments of this invention overcome these and other problems. Afabrication method begins in FIG. 2 with a Silicon seed wafer 30 and aSilicon handle wafer 40. The wafers 30 and 40 can be of any conventionalsize and thickness. In other embodiments the wafers 30 and 40 can becomposed of, for example, SiGe, or a Group III-V, or a Group II-VI wafermaterial.

FIG. 3 shows the formation on the seed wafer 30 of an insulator stripepattern for aspect ratio trapping (ART) in preparation for at least oneof SiGe, Ge, III-V epitaxy. A Silicon oxide layer 42 is formed on thehandle wafer 40 (labeled in the Figures as a buried oxide (BOX) layerfor convenience). In the ART technique a dielectric layer 32, e.g.,SiO₂, Si₃N₄ or SiO_(x)N_(y), is grown on the surface of the seed wafer30 and then parallel trenches 34 are etched through the dielectric layer32 to the surface of the seed wafer 30. The trench width corresponds tothe desired width of the Fins that will be formed. Suitable Fin widthsare in a range of about 4 nm to about 20 nm, with about 6 nm to about 10nm being one exemplary desired range of widths. The trench depthpreferably has an aspect ratio of at least 1:2 (width to depth), buthigher aspect ratios of 1:10 to 1:30 are preferred. A portion of thedielectric layer 32 and material that will fill the trenches will besubsequently removed. In general the trench depth will be greater than adesired final Fin height (that may be, for example, in a range of about30 nm to about 100 nm).

In FIG. 4 a selective epitaxial growth (SEG) process is performed. Inaddition to the various epitaxial growth process apparatus that werementioned above, the embodiments of this invention can also usemetalorganic chemical vapor phase deposition (MOCVD) and metalorganicvapor phase epitaxy (MOVPE) to grow a desired semiconductor material(e.g., SiGe, Ge, Group III-V, Group II-VI) epitaxial film 36 in thetrenches 34 that define the ART insulator stripe pattern. As can be seenthere will exist at the trench bottoms some dislocation defects 36A inthe epitaxial film 36 arising from initial semiconductor growth alongcertain preferred angles (e.g., 60°) depending on the semiconductormaterial. The defects will generally propagate until they encounter thetrench side walls. Above this initially grown volume of semiconductormaterial the epitaxial film with be (ideally) substantially defect free.The thickness of that portion of the filled trench that contains themajority of the dislocation defects can be a function of at least thetype of semiconductor material used to fill the trench, the selected SEGprocess and the trench width. In general the thickness of the portion ofthe filled trench that contains the majority of the dislocation defectscan be twice the trench width.

FIG. 5 shows a result of a selective removal of the top-most portion ofthe dielectric layer 32 and the epitaxial film 36 that fills thetrenches 34. CMP is one preferred technique to planarize and polish thetop of the seed wafer structure in preparation for a wafer bondingprocedure. It can be noted that the dislocation defects 36A are stillpresent in the semiconductor epitaxial film at the trench bottoms.

FIG. 6 shows a result of the deposition of a dielectric film 38 (e.g.,an oxide or a nitride compatible with the Silicon oxide layer 42 of thehandle wafer 40) over the planarized and polished top of the seed wafer30 structure shown in FIG. 5. Silicon oxide is the preferred dielectricmaterial for the layer 42.

FIG. 7 shows a result of a wafer bonding operation wherein the seedwafer structure formed thus far is inverted and the top surface of thedielectric film 38 is placed in contact with the top surface of theSilicon oxide layer 42. Note that the Silicon oxide layer 42 need not beformed or present prior to this step. During the wafer bondingoperation, which is a well-known technique, heat and pressure areapplied to the two structures to be bonded in order to bond or fusetogether the dielectric film 38 and the Silicon oxide layer 42. Notethat after the wafer bonding operation the Silicon oxide layer 42 may bereferred to as being a “buried” oxide layer.

FIG. 8 illustrates the performance of a material removal operation thatremoves the substrate of the seed wafer 30 and that portion of the ARTepitaxy and trenches containing the dislocation defects 36A. Thematerial removal operation is performed to achieve the desired height ofFins 44 (composed of, for example, one or more of SiGe, Ge and GroupIII-V material) relative to the top surface of the bonded BOX layer 42and dielectric film 38 that now form a BOX layer. In practice the seedwafer substrate 30 may have a thickness of about 875 μm and thedielectric material layer 32 that contains the trenches 34 may have athickness of about, for example, 100 nm to about 200 nm. In order tofacilitate the removal of this substantial amount of material it ispreferred to use a multi-step material removal process such one based onan initial grinding operation to remove the bulk of the material, andthen performing a lapping process followed by a CMP process to achievethe final desired Fin height and surface quality.

A next step removes the dielectric (insulator) material 32 that existsbetween the Fins 44 leaving free-standing Fin structures that can befurther processed as needed to form FinFETs and any other types ofFin-based devices for a semiconductor chip of interest. The dielectricmaterial removal process is specific to the type of dielectric material32 that is used for the ART process. Examples of suitable and compatibledielectric material removal processes, selected so as not to have adetrimental effect on shape and/or surface quality of the Fins 44,include selective reactive ion etching (RIE) and selective wet etching.

It can be appreciated that as a result of the material removal processshown in FIG. 8 that the portion of the epitaxial semiconductor material36 deposited at and near to the bottom of the trenches 34, i.e., thatportion containing the majority of the dislocation defects 36A, isphysically abraded away and does not form a part of the final Finstructures 44. As a result the problem discussed above that is relatedto crystalline defects in the Fins is addressed and overcome. Further,the use of the ART technique in conjunction with the preferred waferbonding technique addresses and overcomes the Fin patterning issues thatwere discussed above, such as those related to Fin taper, Fin sidewallroughness, RIE damage and post-RIE cleaning. In essence, no damage tothe Fins 44 occurs due to any Fin formation RIE which is not required bythe method in accordance with this invention.

FIG. 9 shows an embodiment further in accordance with this inventionwhere each channel Fin material can be chosen for NFET and PFET asneeded. FIG. 9A shows the seed wafer 30 with a set of trenches 34 formedin the dielectric material layer 32 as in FIG. 3. FIG. 9B shows a resultof application of a first mask (Mask_1) to a first subset of thetrenches 34 and the deposition by selective epitaxial growth (SEG) of adesired PFET channel semiconductor material into an unmasked secondsubset of the trenches 34. As a non-limiting example the PFET channelsemiconductor material could be SiGe. FIG. 9C shows a result of aremoval of the first mask and the application of a second mask (Mask_2)to the second subset of the trenches 34, followed by the deposition bySEG of a desired NFET channel semiconductor material into the nowunmasked first subset of the trenches 34. As a non-limiting example theNFET channel semiconductor material could be InGaAs. Processing thencontinues as was described for FIGS. 5, 6, 7 and 8 to perform the CMPprocedure on the semiconductor material deposited by SEG, the growth ofthe dielectric film 38, the inversion of the seed wafer 30 and the waferbonding of the seed wafer 30 to the handle wafer 40, and the removal ofthe seed wafer 30 and a portion of the ART structure as in FIG. 8. Thislatter step also removes the portion of the semiconductor material atthe trench bottoms having the high concentration of dislocation defects36A. The result, shown in FIG. 9D, is a structure having high qualityfirst Fins comprised of SiGe and second Fins comprised of InGaAs thatare disposed over the common dielectric layer comprised of thedielectric film 38 and the BOX layer 42.

In FIG. 9 the masking and SEG steps could be performed in either theorder shown or in a reverse order to deposit the NFET channel materialfirst and then the PFET channel material. Furthermore, in some casesthree or more masks could be used in conjunction three of more SEGoperations in order to provide three of more FINFET channel materialinstances on the same common dielectric layer comprised of thedielectric film 38 and the Silicon oxide layer 42.

It is noted that any one of the structures shown in FIGS. 2-9 could beviewed as an intermediate structure formed during the overall process ofproviding the Fins 44 on the common insulator layer.

It is to be understood that although the exemplary embodiments discussedabove with reference to FIGS. 2-9 can be used on common variants of theFET device including, e.g., FET devices with multi-fingered FIN and/orgate structures and FET devices of varying gate width and length.Moreover, transistor devices can be connected to metalized pads or otherdevices by conventional ultra-large-scale integration (ULSI)metalization and lithographic techniques.

Integrated circuit dies can be fabricated with various devices such as afield-effect transistors, bipolar transistors, metal-oxide-semiconductortransistors, diodes, resistors, capacitors, inductors, etc., havingcontacts that are formed using methods as described herein. Anintegrated circuit in accordance with the present invention can beemployed in applications, hardware, and/or electronic systems. Suitablehardware and systems in which such integrated circuits can beincorporated include, but are not limited to, personal computers,communication networks, electronic commerce systems, portablecommunications devices (e.g., cell phones), solid-state media storagedevices, functional circuitry, etc. Systems and hardware incorporatingsuch integrated circuits are considered part of this invention. Giventhe teachings of the invention provided herein, one of ordinary skill inthe art will be able to contemplate other implementations andapplications of the techniques of the invention.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

The corresponding structures, materials, acts, and equivalents of allmeans or step plus function elements in the claims below are intended toinclude any structure, material, or act for performing the function incombination with other claimed elements as specifically claimed. Thedescription of the present invention has been presented for purposes ofillustration and description, but is not intended to be exhaustive orlimited to the invention in the form disclosed. Many modifications andvariations will be apparent to those of ordinary skill in the artwithout departing from the scope and spirit of the invention. Theembodiment was chosen and described in order to best explain theprinciples of the invention and the practical application, and to enableothers of ordinary skill in the art to understand the invention forvarious embodiments with various modifications as are suited to theparticular use contemplated.

As such, various modifications and adaptations may become apparent tothose skilled in the relevant arts in view of the foregoing description,when read in conjunction with the accompanying drawings and the appendedclaims. As but some examples, the use of other similar or equivalentsemiconductor fabrication processes, including deposition processes,etching and other material removal processes may be used by thoseskilled in the art. Further, the exemplary embodiments are not intendedto be limited to only those semiconductor materials, dielectrics, layerthicknesses and the like that were specifically disclosed above. Any andall such and similar modifications of the teachings of this inventionwill still fall within the scope of this invention.

What is claimed is:
 1. A method, comprising: providing a first substratehaving a planar top surface; forming an insulator layer on the planartop surface of the first substrate; forming a plurality of trencheswithin the insulator layer, where the plurality of trenches extendthrough the insulator layer from a top surface of the insulator layer tothe planar top surface of the first substrate, where a width of a trenchformed in the insulator layer corresponds to a width of a semiconductorFin structure that will be formed in the trench and where a depth of thetrench is greater than a desired final height of the semiconductor Finstructure; filling the trenches that are disposed in the insulator layerusing an epitaxial growth process with at least one type ofsemiconductor material, where the semiconductor material that fills eachtrench extends from the top surface of the insulator layer to the planartop surface of the first substrate; planarizing tops of the filledtrenches and forming a first layer of dielectric material on a resultingplanarized surface; inverting the first substrate to place the firstlayer of dielectric material in contact with a second layer ofdielectric material disposed on a second substrate; bonding the firstsubstrate to the second substrate through the first layer of dielectricmaterial and the second layer of dielectric material to form a commonlayer of dielectric material, wherein the semiconductor material thatfills each trench extends between and terminates on a surface of thecommon layer of dielectric material and the planar top surface of thefirst substrate; removing the first substrate and a first portion of thefilled trenches to leave a second portion of the filled trenchesdisposed upon the surface of the common layer of dielectric material,where the first portion of the filled trenches contains dislocationdefects in the semiconductor material resulting from the epitaxialgrowth process; and removing the insulator layer orthogonal to thesurface of the common layer of dielectric material to leave a pluralityof Fin structures disposed upon the surface of the common layer ofdielectric material, where each Fin structure corresponds to one of thefilled trenches and has the same width at a top and a bottom of the Finstructure.
 2. The method of claim 1, where filling the trenches fillsthe trenches with at least one of Ge, SiGe Group III-V and a Group II-VIsemiconductor material.
 3. The method of claim 1, where filling thetrenches fills a first subset of the trenches with a first semiconductormaterial selected for forming PFETs, and fills a second subset of thetrenches with a second semiconductor material selected for formingNFETs.
 4. The method of claim 1, where removing the first substrate anda first portion of the filled trenches is performed as a multi-stepprocess comprised of at least grinding followed by chemical mechanicalpolishing.
 5. The method of claim 1, where the epitaxial growth processis one of metalorganic chemical vapor phase deposition, metalorganicvapor phase epitaxy and molecular beam epitaxy.
 6. The method as inclaim 1, where planarizing tops of the filled trenches comprises using achemical mechanical polishing technique.
 7. The method of claim 1, whereproviding the first substrate supporting an insulator layer havingtrenches formed therein and filling the trenches using an epitaxialgrowth process is carried out as part of an aspect ratio trappingprocedure.
 8. The method of claim 1, where the insulator layer iscomprised of SiO₂.
 9. The method of claim 1, where the insulator layeris comprised of Si₃N₄.
 10. The method of claim 1, where the insulatorlayer is comprised of Si₃O_(x)N_(y).